The invention relates to a tomographic apparatus for producing transverse layer images of a radiographic subject, comprising a measuring arrangement comprising an x-ray source which produces an x-ray beam penetrating the radiographic subject, and whose cross-sectional extent perpendicular to the layer plane is equal to the layer thickness, and a radiation receiver which determines the intensity of radiation behind the subject, such apparatus further comprising a driving means for the measuring arrangement for producing rotational movements of the x-ray measuring arrangement, a measured value converter for transforming the signals supplied by the radiation receiver into a layer image, and a housing for the measuring arrangement which has an opening extending through it for receiving a patient supporting device with a patient.
For generating the layer image, the rotational movements can be effected in small equidistant angular amounts in alternating succession with linear displacements of the measuring arrangement along a straight line path perpendicular to the central ray of the x-ray beam, when a single radiation detector is used as the radiation receiver. However, it is also possible to omit the linear scanning movements if the radiation receiver is constructed of a plurality of radiation detectors whose signals are simultaneously processed by the measured value converter, and if the x-ray beam is of a fan-shaped configuration and strikes all the detectors simultaneously.
A tomographic apparatus of this type is known from U.S. Pat. No. 3,778,614. In the case of this known tomographic apparatus, a couch or support for the patient is present in the opening of the housing of the measuring arrangement and extends therethrough. As a result, the couch is also reproduced on the x-ray image.